6. A bay mare which had been in foal to Matopo for some months miscarried. Here—if there is anything in the direct infection theory—the unused germ-cells of the zebra had a better chance than usual of reaching the ova from which future offspring are to arise, yet neither of the two foals which this mare subsequently produced to a thoroughbred horse “in any way suggests a zebra.”
The above is the record of the successful experiments which have been tried at Penycuik, with a view of throwing light on the existence of telegony in the Equidae. Experiments have also been made with other animals, such as rabbits, dogs, pigeons, fowls, and ducks. Space allows us to quote but one. Six white doe rabbits, all of which had borne pure white offspring to white bucks, were crossed with wild brown rabbits. The result was forty-two young rabbits, all of a bluish-black color, which in a very short time turned to a brown. These, at the time of writing, were about half grown, and Professor Ewart tells us that it is almost impossible to distinguish them from a full-blooded wild rabbit kept in the same inclosure. The half-breeds, however, were tamer and slightly lighter in color. The mother does next bred with white bucks again, and in every case bred true. The pure white young showed no trace of throwing back to a previous sire.
A phenomenon somewhat similar to telegony, and one which seems at present quite unexplained, is that a hen which has been crossed with a cock of another breed often lays eggs whose shell is no longer like that of its own breed, but in color, and frequently in texture, resembles that of the breed with which it has been crossed. When one calls to mind that the shell is deposited by a special shell-gland which is in no way connected with the ovary, but is a part of the quite distinct oviduct, and that the change in the color of the eggshell must be caused by some change brought about in this gland by cross-fertilization, we begin to recognize how mysterious and inexplicable are many of the problems which affect breeding.
Throughout his account of his experiments Professor Ewart is extremely cautious in claiming to prove anything, but we think he has justified his claim to have shown that telegony by no means always occurs, as many breeders believe. His experiments so far support the view of Continental mule breeders, that telegony, if it takes place, occurs very seldom. But the experiments are not complete, and it is much to be hoped that they may be continued. If it should subsequently appear that out of fifty pure-bred foals from dams which have been previously mated with the zebra no single instance of telegony be found, the doctrine may surely be neglected by breeders; and if in the experiments which are now being carried out with various other mammals and birds telegony does not occur, the doctrine may be relegated to the ‘dumping-ground’ of old superstitions. The present state of the matter may be summed up in the professor’s own words: “The experiments, as far as they have gone, afford no evidence in support of the telegony hypothesis.” Nothing has occurred which is not explicable on the theory of reversion.
There is no factor in breeding of more importance than prepotency, and none which is more difficult to estimate. The term is necessarily a relative one, and, further, it may affect some characters and not others. Often it must go undetected, as in the case of the leader of a herd of wild cattle, who may be highly prepotent, but whose prepotency, unless he is mated with members of another herd displaying different characters, may pass unnoticed. Breeders claim to be able to produce cattle so prepotent that they will produce their like, however mated. A well-known dealer in highly-bred ponies used to boast that he had a filly so prepotent that, though she were sent to the best Clydesdale stallion in Scotland, she would throw a colt showing no cart-horse blood. Prepotency is usually obtained by inbreeding, which up to a certain point fixes the character of a race, and in all cases tends to check variation and reversion—the Jews, for instance, as a race are strongly prepotent—but there is no doubt that it may also arise as a sport, and this is probably its more usual origin in a state of Nature. Professor Ewart, however, believes that inbreeding is much commoner among wild animals than has usually been conceded, and he holds the opinion that the prepotency so induced has played a considerable part in the origin of species. This, if true, would to some extent take the place of Romanes’ ‘physiological selection’; for Romanes also thought that, though of great importance, variation and natural selection were insufficient to account for the origin of species without some factor which would help to mitigate the swamping effect of intercrossing—some such agency as the fences of modern farms and cattle ranches—without which the famous cattle breeds of the world would soon disappear in a general ‘regression toward mediocrity.’
In inbreeding the great difficulty of the breeder is to know when to stop. Carried too far it undoubtedly leads to degeneracy. In the ‘Domesticated Animals of Great Britain,’ Low records the case of a gentleman who inbred foxhounds to such an extent that “the race actually became monstrous and perished.” Hogs, if too closely inbred, grow hair instead of bristles; their legs become short and unable to support the body; and not only is their fertility diminished, but the mothers can not nourish the young.
So far as is known, no direct investigations have been made to test how far inbreeding may be carried in the Equidae; but, on the other hand, the breeding of race-horses may perhaps be looked upon as a gigantic experiment in this direction. Our English thoroughbreds can be traced back to a few imported sires—the Byerly Turk, imported in 1689; the Darley Arabian, in 1710; and the Godolphin Arabian, in 1730. Since then, by careful breeding and nutrition, they have increased on an average some eight or nine inches in height. There is, however, a widely spread impression that at present there is a marked deterioration in the staying power and in the general ‘fitness’ of the racer. The falling off is further shown by a fact commented on by Sir Walter Gilbey—viz., “the smallness of the percentage of even tolerably successful horses out of a prodigious number bred at an enormous outlay.” In support of this he quotes a sentence from the Times (December 27, 1897), referring to a sale in which thirty-two yearlings had been sold for 51,250 guineas: “These thirty-two yearlings” (said the Times) “are represented by two winners of five races, Florio Rubattino and La Reine, who have contributed about 2,000l. to the total cost; and there is not, so far as can be known, a single one of the thirty others with any prospect of making a race-horse.”
If, then, it is true that the English race-horse is on the down grade, what steps should be taken to arrest this descent? Sir Everett Millais restored a pack of basset hounds by crossing them with a bloodhound, the original forefather of bassets. The resulting pups were bassets in form, but not quite bassets in color; when, however, these cross-breeds were mated with bassets the majority of the pups turned out to be perfect bassets both in shape and coloration. This indicates that one way to rejuvenate the race-horse would be to have recourse to a new importation of the best Arab mares that the plains of Arabia can produce. Breeders hesitate to adopt this course, because their present breed is not only larger but, over very short distances, fleeter than its forefathers. The shortening of the course in recent years is probably a further sign of the degeneracy of our present racers. Were new blood introduced and more three- or four-mile races instituted, we should doubtless soon have a return to the champion form of bygone days. Another method would be to import some of the racers of Australia or New Zealand and cross them with the home product. Different surroundings, food, etc., soon influence the constitution, and this being so, it would be advisable to select those horses of pure descent which have been longest subjected to these altered conditions. Thus the chance of reversion occurring would be increased.
It has been noticed more than once in the preceding pages that a young animal showing reversion is strong and vigorous. It is the belief of dog breeders that those members of an inbred litter which show reversion are the strongest and best. Similarly, experience shows that if an inbred sire and dam produce a dun-colored striped foal it almost always turns out well. Reversion is accompanied by a rejuvenescence; it is as though the young animal had appeared at an earlier period in the life history of the race, before the race had undergone those changes in the way of deterioration which so often accompany inbreeding.
Wild animals are frequently thought to be prepotent over tame ones, but of the eleven zebra-hybrids bred at Penycuik only two took markedly after their sire, the zebra Matopo.[B] There are other experiments recounted which tell the other way, and at present this matter remains in a state of considerable uncertainty.